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<head>
    <meta charset="UTF-8">
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    <title>Document</title>
</head>

<body>
    <button id="ldh">刘德华</button>
    <button id="zxy">张学友</button><br>
    <img src="1.gif" alt="">
    <script>
        //获取元素
        let ldh = document.getElementById('ldh')
        let zxy = document.getElementById('zxy')
        var img = document.querySelector('img')
        zxy.onclick = function () {
            img.src = "640.gif"
        }
        ldh.onclick = function () {
            img.src = "1.gif"
        }
    </script>
</body>

</html>